This application is related to two U.S. applications filed on Mar. 6, 1998 in the name of Pontus Wallentin entitled xe2x80x9cTelecommunications Inter-Exchange Measurement Transferxe2x80x9d Ser. No. 09/035,827 and xe2x80x9cTelecommunications Inter-Exchange Congestion Controlxe2x80x9d Ser. No. 09/035,788; both of which are hereby incorporated by reference herein.
1. Technical Field of the Invention
The present invention generally relates to a mobile telecommunications network and, in particular, to a system and method used in a mobile telecommunications network for load balancing ongoing calls between different base station controllers.
2. Description of Related Art
A mobile telecommunications network having an architecture according to the Global System for Mobile Communications (GSM) specification includes a multitude of cells. The cells effectively divide an arbitrary geographic area into a plurality of contiguous radio coverage areas; each of which is served by a base transceiver station (BTS). The BTS serves each cell by utilizing a limited number of traffic channels that are controlled by a base station controller (BSC). The BSC is generally used to supervise and control a group of the BTSs.
The BSC may have a feature known as xe2x80x9cCell Load Sharingxe2x80x9d to increase the capacity and operating performance of the network by effectively balancing the ongoing call loads between the cells that are adjacent to one another. For example, at any time a particular cell may have a high ongoing call load, while adjacent cells have low ongoing call loads, thus triggering the xe2x80x9cCell Load Sharingxe2x80x9d feature of the base station controller to balance the various call loads between the different cells. The BSC balances the various call loads by transferring some of the ongoing calls from the cell having the high ongoing call load to the adjacent cell(s) having the low ongoing call load. Of course, the ongoing call load for any cell is constantly changing due mainly to origination of new calls and handovers of calls from traveling mobile terminals.
However, the xe2x80x9cCell Load Sharingxe2x80x9d feature currently used will operate only with respect to the cells or base transceiver stations that are controlled by one base station controller. Thus, if a cell associated with a different base station controller is adjacent to the cell controlled by another base station controller, then no balancing of the ongoing calls can be completed, because the required information is not communicated between the different base station controllers.
Accordingly, there is a need for a method and system used in a mobile telecommunications network for load balancing ongoing calls between adjacent cells controlled by different base station controllers. There is also a need for a system and method for transmitting load indication messages between different base station controllers. These and other needs are satisfied by the system and method of the present invention.
The present invention is a method and system for load balancing used in a mobile telecommunications network. The load balancing system includes a mobile services switching center and a first base station controller coupled to the mobile services switching center for managing a first plurality of cells. The load balancing system further includes a second base station controller coupled to the mobile services switching center for managing a second plurality of cells, where one cell of the first plurality of cells is adjacent to one cell of the second plurality of cells. The second base station controller includes a processor responsive to receiving a first load indication message from the first base station controller in order to determine whether to handover at least one ongoing call from the one cell of the second base station controller to the one cell of the first base station controller.
In accordance with the present invention, a system and method are provided for balancing an ongoing call load across a boundary between adjacent cells that are controlled by different base station controllers.
Also in accordance with the present invention, a system and method are provided that have a base station controller generating a load indication message whenever the number of available traffic channels within a cell changes so as to exceed or fall below a predetermined threshold.
Further in accordance with the present invention, a method and system are provided for utilizing a load indication message in a different and more advantageous manner than was intended by the GSM specification.